Highly Efficient Copper Sulfide‐Based Near‐Infrared Photothermal Agents: Exploring the Limits of Macroscopic Heat Conversion

Abstract

Among the foreseeable therapeutic approaches at the cellular level, nanoplatform‐driven photothermal therapy is a thriving tool for the selective eradication of malignant tissues with minimal side effects to healthy ones. Hence, chemically versatile, near‐infrared absorbing plasmonic nanoparticles are distinctly appealing and most sought after as efficient photothermal agents. In this work, a straightforward method to synthesize monodisperse PEGylated copper sulfide nanoparticles of pure covellite (CuS) phase, featuring strong localized surface plasmonic resonance absorption in the near‐infrared and flexible surface chemistry, imparted by monomethyl ether polyethylene glycol molecules, is developed and optimized. These nanoparticles show a remarkable photothermal heat conversion efficiency (HCE) of 71.4%, which is among the highest for CuS systems and rivals that of plasmonic noble metal nanostructures. Moreover, through critical evaluation and mathematical modeling of the material's properties and measurement methodology, it is assessed that the calculated HCE values drastically depend on experimental conditions such as wavelength‐dependent solvent absorption properties, sol concentration, and optical path. These findings are of paramount relevance to the photothermal community, since they call for a standardization of the procedure for the evaluation of the HCE of proposed photothermal agents, in order to make the reported values universally and reliably comparable.

Polyaniline Nanovesicles for Photoacoustic Imaging‐Guided Photothermal‐Chemo Synergistic Therapy in the Second Near‐Infrared Window

“…Hence, the key to achieving PAI and PTT in the NIR‐II window depends on the design and development of suitable exogenous imaging contrast agents and photothermal (PT) agents. [ 15–18 ] At present, most NIR‐II photothermal agents are inorganic materials, such as gold nanoassemblies, [ 19,20 ] copper sulfide, [ 21,22 ] and carbon nanotubes. [ 23 ] Besides, quantum dots [ 24 ] and rare‐earth doped nanoparticles [ 6 ] have also been used as stable photothermal agents.…”

Plasmonic Copper Sulfide Nanoparticles Enable Dark Contrast in Optical Coherence Tomography

“…As we highlighted in a previous study, [28] the methods for the experimental determination of η are usually affected by experimental conditions such as dispersant absorption properties and concentration of the dispersed NPs. Thus, η is really a parameter describing macroscopically the system, rather than providing a picture at the microscopic scale.…”

“…Copper sulfide NPs feature a LSPR conveniently centered in the NIR, even when their size is below 10 nm . This translates to an almost complete light absorption, as it minimizes their scattering efficiency . Because the LSPR arises from the motion of vacancies delocalized in the material's valence band, the spectral position of this feature can be controlled by various means, such as NP size, morphology and stoichiometry (Cu x S, where x varies from 1 to 2) …”

“…[26,27] This translates to an almost complete light absorption, as it minimizes their scattering efficiency. [28] Because the LSPR arises from the motion of vacancies delocalized in the material's valence band, the spectral position of this feature can be controlled by various means, such as NP size, morphology and stoichiometry (Cu x S, where x varies from 1 to 2). [29][30][31] Following this reasoning, capitalizing on the negligible light scattering of small CuS plasmonic NPs, we report on the first example of OCT dark contrast agents operating in NIR-II.…”

PVP-coated Sb2Se3 nanorods as nanotheranostic agents for photoacoustic imaging and photothermal therapy in NIR-I bio-windows

“…[1][2][3][4][5] Currently, diverse types of nanotherapeutics, such as organic dye ICG; inorganic nanoparticles Pd, Ge, Au, black phosphorus QDs, CuS, MoS 2 , Bi 2 S 3 and WO 3ÀX nanocrystals; organic semiconducting polymer nanoparticles (SPNs) and ppy nanoparticles, have been investigated for NIR PTT. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] Antimony selenide (Sb 2 Se 3 ) as a simple, low toxicity, lowcost p-type semiconductor material with broad absorbance ranging from the UV to the NIR region has many potential applications in photovoltaic, thermoelectric, and phase-change memory devices. [21][22][23] Owing to these excellent properties, much effort has been devoted to the fabrication of Sb 2 Se 3 and its photovoltaic applications, rarely have this material been explored for its biomedical applications.…”